A cloud of tiny white insects lifting off a plant when you brush past is the classic sign of whiteflies. They are worth acting on early. UC IPM says management is difficult once populations are high, and the stage that does most of the damage sits still on the leaf undersides where it is easy to miss.

The good news is that a houseplant is a small, contained target. Inspection, washing and steady follow-up can bring numbers down before you reach for anything stronger.

Confirm it is whitefly

Whiteflies are not true flies. UC IPM places them with aphids, scales and mealybugs, which all suck sap. Check these features:

  • Adults. RHS describes small white-winged insects about 1.5 mm (1/16 in) long that fly up when the plant is disturbed. Maryland Extension says they look like tiny white moths, often dusted with powdery white wax.
  • Nymphs. Turn the leaf over. Maryland describes flat disks on the undersides. Colorado State calls them scale-like, translucent and immobile, and easy to overlook.
  • Eggs. RHS says females lay greyish white eggs on the underside of leaves, singly or in circles.
  • Black nymphs. RHS notes that nymphs that have turned black have probably been parasitised by an Encarsia wasp and are dead.

The species most often found indoors is the greenhouse whitefly, Trialeurodes vaporariorum. Colorado State lists it on poinsettia, ivy, hibiscus and lantana. RHS adds pelargonium, fuchsia, chrysanthemum and gerbera.

Look-alikes

What you seeMore likelyHow to tellSource
White specks on the upper leaf surface that do not moveAphid cast skinsWhiteflies and their nymphs sit on the undersideRHS, UC IPM
White cottony tufts along veins and where leafstalks join stemsMealybugsNo winged cloud when disturbed; check crevices and leaf basesUC IPM
Dark flies running over the potting mixFungus gnatsGnats breed in the mix, not on leavesUC IPM
Brown or grey bumps on stems and leavesSoft scaleMostly stationary under a waxy shell; can be scraped offUC IPM, Colorado State

If the flies are dark and come from the mix, read our fungus gnat guide instead.

Honeydew and sooty mold

All whitefly stages feed by sucking sap. UC IPM says they excrete the excess as drops of honeydew, so leaves below them turn sticky. Black sooty mold then grows on the honeydew. Heavy infestations can cause yellowing, leaf drop, stunting and an unthrifty-looking plant, according to UC IPM and Maryland.

Stickiness alone does not prove whiteflies. UC IPM lists aphids, mealybugs and soft scales as honeydew producers too. Our citrus honeydew guide walks through finding which insect is responsible.

Where whiteflies come from

Colorado State says whitefly infestations on houseplants are almost always established from plants recently bought or received as gifts. Some whiteflies can also move onto plants during warm summer months. UC IPM advises inspecting plants closely after bringing them back indoors from outside.

Warmth speeds them up. RHS gives the life cycle as about three weeks at 21 °C (70 °F), compared with several months at 10 °C (50 °F). Colorado State says eggs hatch in three to seven days, nymphs feed for two to four weeks, and adults may lay eggs for two months. Generations overlap, which is why one treatment rarely finishes the job.

Control, from least toxic up

Pick the plant up and isolate it first. UC IPM advises isolating any houseplant with an insect problem immediately so it cannot spread.

1. Remove and wash

  • Pick off infested leaves. UC IPM says hand removal of leaves heavily infested with nymphs can reduce populations.
  • Wash the plant. UC IPM suggests washing eggs and crawling young off with water. Colorado State says a vigorous jet of water helps control many houseplant pests. Pay attention to leaf undersides.
  • Vacuum adults. Colorado State says small hand-held vacuums help, and that on small plants adults can be eliminated this way.

2. Yellow sticky cards

Yellow sticky cards trap the winged adults. UC IPM says cards in individual pots can sometimes reduce populations. Both UC IPM and RHS say they are most useful for monitoring. Colorado State warns that trapping alone will not eliminate whiteflies because the young stay on the plant.

Place a card near the infested leaves. If weekly catches fall, your other steps are working.

3. Insecticidal soap, horticultural oil or neem

These are the first products every source turns to. They act on contact, so coverage matters.

  • Soap. Maryland and Clemson both say to spray the leaf undersides with an insecticidal soap labeled for the plant. Clemson warns some plants are sensitive to soap sprays, including ivy, maidenhair fern and dieffenbachia.
  • Oil and neem. Colorado State says horticultural oils, neem insecticides and soaps may control nymphs on leaves. UC IPM says these less-toxic products control only the whiteflies they directly hit, so repeat applications may be needed.
  • Timing. UC IPM advises using soaps or oils on plants that are not drought-stressed, and below 32 °C (90 °F), to avoid burn.

For more on these two product types, see our neem oil vs insecticidal soap comparison.

4. Other insecticides, by label only

Colorado State lists pyrethrins as the most effective chemical control for adult whiteflies. It also says the systemic imidacloprid is highly effective, but can harm non-target insects, especially bees. Clemson lists soil-applied imidacloprid granules for houseplants. UC IPM adds that imidacloprid can trigger spider mite outbreaks.

Colorado State’s rule is the one to keep: only use pesticides specifically labeled for houseplants, and do not use a product if your plant or pest is not on the label. If possible, spray the plant outdoors, as UC IPM suggests.

5. Know when to discard

Maryland says heavily infested plants should be discarded. UC IPM agrees that a large infestation may be best handled by disposing of the plant. Colorado State notes a relatively short host-free period eliminates greenhouse whitefly, so clearing out an infested plant can end the cycle.

Biological control is mostly for larger plantings. Colorado State says Encarsia formosa works on greenhouse whitefly only if average temperatures stay at 22–24 °C (72–75 °F) or above.

Prevention

  • Quarantine new plants. Colorado State advises at least three weeks in a separate area. Clemson suggests six weeks, with weekly checks of leaf undersides under a 10x hand lens.
  • Inspect before you buy. UC IPM says to reject plants showing insect infestations.
  • Check summered plants. Inspect closely before bringing them back indoors, then monitor for a few weeks (UC IPM).
  • Keep a card out. A yellow sticky card near susceptible plants flags new arrivals early.

Plant-specific guides

For a whitefly problem on a wax plant, see whiteflies on hoya. For the wider range of houseplant pests and how treatments compare, read our houseplant pest treatment guide.

References